See my other comment. In the competitions discussed in The Selfish Gene, PD strategies are allowed to have memory and the simulation is run thousands of times p

See my other comment. In the competitions discussed in The Selfish Gene, PD strategies are allowed to have memory and the simulation is run thousands of times per round. However it is pretty consistently the case that long-term memory is not an outright win for either the competitor or the opponent, compared to the simple "tit-for-tat" strategy which only remembers the previous iteration. Of course the PD only models certain kinds of human/animal interactions. Knowing that a particular person is a cheater or is vindictive or whatever is obviously important for evolutionary strategy as a whole. But the question is more about heterogenous populations. Is there an optimal strategy that wins more than any other across a wide range of opposing strategies, including if everyone else is actually using the same strategy?